The invention relates to a pressure vessel comprising a heat exchanger for a cryogenically stored medium, in particular for use in a motor vehicle, in particular as a pressure tank for hydrogen.
It is already known to use hydrogen as a fuel for motor vehicles and, for this purpose, to store the latter in a pressure tank under positive pressure. Pressure tanks of this type can consist of steel or lightweight metal. For a relatively high filling pressure, for example, such a substantially cylindrical lightweight metal tank can be wrapped with a fiber composite material comprising, for example, glass and/or carbon fibers.
For the handling of cryogenically stored fuel, it is advantageous if a heat exchanger is accommodated in the pressure vessel. This is described by WO 2006/133816 A1. The storage vessel described there for cryogenically stored hydrogen has a condensing line with heat exchanger which is used to supply gaseous cryogenic medium which, in the heat exchange, is cooled down against the stored cryogenic medium. However, in pressure vessels for cryogenically stored medium, also called cryotanks, it is also usual to accommodate heat exchangers which are used only to increase the pressure of the medium in the cryotank as necessary by means of an input of heat from outside, in order for example to accelerate removal of the medium. Such a heat exchanger, which has no opening to the interior of the pressure vessel or cryotank and is supplied with heat exchange medium only from outside the cryotank, is nevertheless normally operated with the medium stored in the vessel as a heat exchange medium as well, since not many usual heat exchange media are suitable for cryogenic application and since it is therefore simpler then to use the substance already cryogenically stored in the pressure vessel as a heat exchange medium for cryogenic application.
In the event of necessary large-scale production, the most economical production of such a pressure vessel comprising in-tank heat exchanger is important, and this leads to the object of the invention to specify a pressure vessel comprising heat exchanger for cryogenically stored medium which, in a short time and with low costs, can be produced with constant, good quality.
According to the invention, a pressure vessel for a cryogenically stored medium, comprising a cylindrical jacket and rounded-off end faces which are rolled onto the ends of said jacket and which have centrally positioned openings which are closed by welded-in inserts, at least one first insert being provided at least with filling and removal devices, is characterized in that the inserts form bearings, to which at least one in-tank heat exchanger is fitted.
The pressure vessel according to the invention can thus be produced independently of the in-tank heat exchanger. The latter is fixed to the inserts and welded to the latter, which means that the production time and therefore the production costs can be reduced considerably, and the production quality with regard to tightness of the heat exchanger can be guaranteed.
Advantageous embodiments of the invention are characterized in that the in-tank heat exchanger extends in the axial direction from the first insert to a second insert. This can advantageously be implemented in such a way that the in-tank heat exchanger comprises two pipes, a feed pipe and a return pipe, which are fitted individually to the first insert and are mounted together on the second insert via a connecting device, wherein the feed pipe can be charged with cryogenic medium from outside the pressure vessel via a filling opening in the first insert, and, in the further course, the cryogenic medium flows through the feed pipe via the connecting device into the return pipe and from the latter into the pressure vessel via a first outlet opening, or is led out of the pressure vessel through the first insert via an outlet opening in the latter. Beneficially, the first outlet opening is fitted in the return pipe, in the vicinity of the first insert, or in the first insert, while devices of any type carrying further heat exchange media are fitted to the outlet opening outside the pressure vessel. In order to support the heat exchange process between the pipes and the pressure vessel content, it is advantageous if the pipes of the in-tank heat exchanger are provided with heat exchange fins on the outside, at least in some sections. Here, it is very beneficial for the production of the pressure vessel comprising heat exchanger if the circumference of the entire heat exchanger is smaller than the openings in the pressure vessel which are closed by the inserts. Thus, before the mounting of the pressure tank, an insert can already be connected to the in-tank heat exchanger. During the mounting, this insert comprising the heat exchanger is then inserted into the pressure vessel and connected to the latter, while the other insert is subsequently connected to the pressure vessel, closing the pressure vessel and holding the in-tank heat exchanger.
Preferred embodiments of the invention are characterized in that the inserts form bearings, to which the filling and removal devices are fitted. These advantageously extend in the axial direction from the first insert to the second insert. Then, they can comprise two further pipes, a filling pipe and a removal pipe, which are mounted individually on the first insert and are mounted on the second insert via the connecting device. This has the advantage that the mounting of the filling and removal devices can be carried out together and in the same way as the in-tank heat exchanger. To this end, the removal pipe is advantageously fitted or mounted above the filling pipe and the feed pipe is fitted or mounted beside the return pipe on the first insert and on the connecting device such that the four pipes together cover a rectangle arranged horizontally and symmetrically with respect to the mid-axis of the pressure vessel. The corners of this rectangle are located within the areas of the openings of the pressure vessel for this purpose. It is then possible for all four pipes, mounted on the first insert, to be slid into the pressure vessel, corresponding to the above description for the in-tank heat exchanger pipes. In order to reinforce these internal fittings, it is further advantageous if the four pipes are kept at a distance from one another by transverse stiffeners introduced between them. An embodiment which is to be emphasized particularly qualitatively is achieved if the removal pipe, the filling pipe, the feed pipe and the return pipe are drawn seamlessly from a lightweight metal material. These can then be connected particularly reliably in a gas-tight manner to the first insert and to the connecting device by welding if the last-named devices likewise consist of a lightweight metal material, in particular if the liner of the pressure vessel likewise consists of lightweight metal.
Furthermore, it is advantageous if the filling pipe can be charged with cryogenic medium from outside the pressure vessel via a filling opening in the first insert, and, in the further course, the cryogenic medium flows through the filling pipe until in the vicinity of the connecting device and from there into the pressure vessel via a second outlet opening in the filling pipe. In this way, even during the filling operation via the filling pipe, an advantageous exchange of heat between the pressure vessel content and the medium introduced takes place. While the removal pipe advantageously has a removal opening through which cryogenic medium of the pressure vessel content can flow into the removal pipe and, in the further course, the cryogenic medium can flow from the removal pipe through the first insert and can thus be removed outside the pressure vessel. Such a removal device is constructed very simply.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.